Python hmac and C# hmac

Question

We have a python web service. It needs a hash as a parameter. The hash in python is generated this way.

    hashed_data = hmac.new("ant", "bat", hashlib.sha1)
    print hashed_data.hexdigest()

Now, this is how I generate the hash from C#.

    ASCIIEncoding encoder = new ASCIIEncoding();
    Byte[] code = encoder.GetBytes("ant");
    HMACSHA1 hmSha1 = new HMACSHA1(code);
    Byte[] hashMe = encoder.GetBytes("bat");
    Byte[] hmBytes = hmSha1.ComputeHash(hashMe);
    Console.WriteLine(Convert.ToBase64String(hmBytes));

However, I'm coming out with different result.

Should I change the order of the hashing?

Thank you,

Jon

Answer 1

In order to print the result:

• In Python you use: .hexdigest()
• In C# you use: Convert.ToBase64String

Those 2 functions don't do the same thing at all. Python's hexdigest simply converts the byte array to a hex string whereas the C# method uses Base64 encoding to convert the byte array. So to get the same output simply define a function:

public static string ToHexString(byte[] array)
{
    StringBuilder hex = new StringBuilder(array.Length * 2);
    foreach (byte b in array)
    {
        hex.AppendFormat("{0:x2}", b);
    }
    return hex.ToString();
}

and then:

ASCIIEncoding encoder = new ASCIIEncoding();
Byte[] code = encoder.GetBytes("ant");
HMACSHA1 hmSha1 = new HMACSHA1(code);
Byte[] hashMe = encoder.GetBytes("bat");
Byte[] hmBytes = hmSha1.ComputeHash(hashMe);
Console.WriteLine(ToHexString(hmBytes));

Now you will get the same output as in Python:

739ebc1e3600d5be6e9fa875bd0a572d6aee9266